Board Thread:Pokémon Help/@comment-32228622-20170614153355/@comment-30804097-20170614173930

Definitely Mega Gengar (the shiny/Crystal part does not matter). Mega Gengar is wayyyy better than Mega Steelix, although that does not mean you shouldn't use Steelix. Steelix's normal ability is Sturdy, which is better than the Mega Ability. Plus, Gengar is just better.